Hsp33 is a member of a new and highly conserved heat shock protein family in E. coli. In vitro experiments by Dr. Jakob in Dr. Bardwell's laboratory reveal that Hsp33 is an extremely efficient molecular chaperone in protecting unfolding proteins from irreversible aggregation. Depending on the redox state of the environment, Hsp33's chaperone activity is either on or off. Under norinal reducing conditions, Hsp33 is inactive; however, Hsp33 turns into an active folding helper protein when exposed to oxidative stress. This is a stress known to be induced by human phagocytes, the first line of defense in killing invading organisms In vivo experiments support our in vitro findings by revealing that Hsp33 is an important player in protecting prokaryotes from oxidative stress. We are interested in finding the structural mechanism of this novel redox sensitive chaperone function of HSP33. Data collection on BioCARS Station 14-BM-C.